1. Field of the Invention
The present invention relates to a clutch structure, and more particularly to a clutch structure for manual hoists, which is automatically enforced upon an overload operation.
2. Description of Related Art
A manual hoist is a convenient mechanism for hoisting or unloading a heavy object. The manual hoist has a simple structure such that the manual hoist is widely used in many places.
The manual hoist usually includes a handle for sequentially driving a drive device and a wind device for to roll/release a chain or a cable to hoist/unload the heavy object. However, the conventional manual hoist has no clutch structure. Consequently, the operator frequently operates the manual hoist under an overload condition. As a result, the operator is located in a dangerous work place and the use life of the manual hoist is shortened due to an over abrasion.
Consequently, some manual hoist manufacturers provide a clutch structure between the drive device and the wind device for promoting the safety of the manual hoists. The conventional clutch structure of manual hoist includes two ratchets that are laterally abutted each other. A slip is formed between the two ratchets when the manual hoist is overload and the friction between the two ratchets is smaller than the load of the hoist such that the drive device can not drive the wind device to roll chain or cable.
However, a vibration may be occurred between the two ratchets and the two ratchets may be collided during clutching, especially when the hoist is in a heavy load. As a result, the use life of the ratchets is shortened even damaged during operating.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional manual hoist and the clutch structure thereof.